1. Field of Invention
The present invention relates generally to medical devices that support one or more diagnostic or therapeutic elements in contact with body tissue and, more particularly, to medical devices that support one or more diagnostic or therapeutic elements in contact with bodily orifices or the tissue surrounding such orifices.
2. Description of the Related Art
There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
Normal sinus rhythm of the heart begins with the sinoatrial node (or xe2x80x9cSA nodexe2x80x9d) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or xe2x80x9cAV nodexe2x80x9d). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or xe2x80x9cHISxe2x80x9d bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called xe2x80x9cconduction blocksxe2x80x9d) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called xe2x80x9creentry circuits,xe2x80x9d disrupt the normally uniform activation of the left and right atria.
Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called xe2x80x9cmaze procedurexe2x80x9d which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do. It also requires open heart surgery and is very expensive.
Maze-like procedures have also been developed utilizing catheters which can form lesions on the endocardium (the lesions being 1 to 15 cm in length and of varying shape) to effectively create a maze for electrical conduction in a predetermined path. The formation of these lesions by soft tissue coagulation (also referred to as xe2x80x9cablationxe2x80x9d) can provide the same therapeutic benefits that the complex incision patterns that the surgical maze procedure presently provides, but without invasive, open heart surgery.
Catheters used to create lesions typically include a relatively long and relatively flexible body portion that has a soft tissue coagulation electrode on its distal end and/or a series of spaced tissue coagulation electrodes near the distal end. The portion of the catheter body portion that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the intenor of the heart, and then manipulated such that the coagulation electrode contacts the tissue that is to be ablated. Fluoroscopic imaging is used to provide the physician with a visual indication of the location of the catheter.
In some instances, the proximal end of the catheter body is connected to a handle that includes steering controls. Exemplary catheters of this type are disclosed in U.S. Pat. No. 5,582,609. In other instances, the catheter body is inserted into the patient through a sheath and the distal portion of the catheter is bent into loop that extends outwardly from the sheath. This may be accomplished by pivotably securing the distal end of the catheter to the distal end of the sheath, as is illustrated in co-pending U.S. application Ser. No. 08/769,856, filed Dec. 19, 1996, and entitled xe2x80x9cLoop Structures for Supporting Multiple Electrode Elements.xe2x80x9d The loop is formed as the catheter is pushed in the distal direction. The loop may also be formed by securing a pull wire to the distal end of the catheter that extends back through the sheath, as is illustrated in co-pending U.S. application Ser. No. 08/960,902, filed Oct. 30, 1997, and entitled, .xe2x80x9cCatheter Distal Assembly With Pull Wires,xe2x80x9d which is incorporated herein by reference. Loop catheters are advantageous in that they tend to conform to different tissue contours and geometries and provide intimate contact between the spaced tissue coagulation electrodes (or other diagnostic or therapeutic elements) and the tissue.
One lesion that has proven to be difficult to form with conventional devices is the circumferential lesion that is used to isolate the pulmonary vein and cure ectopic atrial fibrillation. Lesions that isolate the pulmonary vein may be formed within the pulmonary vein itself or in the tissue surrounding the pulmonary vein. Conventional steerable catheters and loop catheters have proven to be less than effective with respect to the formation of such circumferential lesions. Specifically, it is difficult to form an effective circumferential lesion by forming a pattern of relatively small diameter lesions. More recently, inflatable balloon-like devices that can be expanded within or adjacent to the pulmonary vein have been introduced. Although the balloon-like like devices are generally useful for creating circumferential lesions, the inventors herein have determined that these devices have the undesirable effect of occluding blood flow through the pulmonary vein.
Accordingly, the inventors herein have determined that a need exists generally for structures that can be used to create circumferential lesions within or around bodily orifices without occluding fluid flow and, in the context of the treatment of atrial fibrillation, within or around the pulmonary vein without occluding blood flow.
Accordingly, the general object of the present inventions is to provide a device that avoids, for practical purposes, the aforementioned problems. In particular, one object of the present inventions is to provide a device that can be used to create circumferential lesions in or around the pulmonary vein and other bodily orifices in a more efficient manner than conventional apparatus. Another object of the present invention is to provide a device that can be used to create circumferential lesions in or around the pulmonary vein and other bodily orifices without occluding blood or other bodily fluid flow.
In order to accomplish some of these and other objectives, a probe in accordance with one embodiment of a present invention includes an elongate body and a helical structure associated with the distal region of the elongate body. In one preferred implementation, a plurality of spaced electrodes are carried by the helical structure. Such a probe provides a number of advantages over conventional apparatus. For example, the helical structure can be readily positioned with the body such that a ring of electrodes is brought into contact with the tissue in or around the pulmonary or other bodily orifice. The helical structure also defines an opening that allows blood or facilitates the formation of a circumferential lesion without the difficulties and occlusion of blood or other fluids that is associated with conventional apparatus.
In order to accomplish some of these and other objectives, a probe in accordance with one embodiment of a present invention includes an elongate body, a loop structure associated with the distal region of the elongate body, and an anchor member associated with the distal region of the elongate body and located distally of the loop structure. In one preferred implementation, a plurality of spaced electrodes are carried by the loop structure. Such a probe provides a number of advantages over conventional apparatus. For example, the anchor member may be positioned within a bodily orifice, such as the pulmonary vein, thereby centering the loop structure relative to the orifice. This allows a circumferential lesion to be created in or around the pulmonary vein or other orifice without the aforementioned difficulties associated with conventional apparatus.
In order to accomplish some of these and other objectives, a probe in accordance with one embodiment of a present invention includes an elongate body defining a curved portion having a pre-set curvature and a control element defining a distal portion associated with the distal region of the elongate body and extending outwardly therefrom and proximally to the proximal end of the elongate body. In one preferred implementation, a plurality of spaced electrodes are carried by the distal region of the elongate body. Such a probe provides a number of advantages over conventional apparatus. For example, the control element may be used to pull the distal region of the elongate body into a loop in conventional fashion. Unlike conventional apparatus, however, the pre-set curvature of the curved portion may be such that it orients the loop in such a manner that it can be easily positioned in or around the pulmonary vein or other bodily orifice so that a circumferential lesion can be easily formed.
The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.